JPS5946867A - Searching system of slight ground-fault point - Google Patents

Abstract

PURPOSE:To detect a slight continuous ground-fault while keeping distribution lines applied with voltage by providing sub-stations plural pieces of which are installed in the distribution lines and transmit the electric signals proportional to the quantity of electricity relating to the ground-fault and a master station which compares successively the electric signals and judges a discontinuous point as a slight ground-fault point. CONSTITUTION:Plural sub-stations (36-1-36-n) consisting of a zero phase current transformer 32 which derives zero phase current and a measuring circuits 34 which measures the secondary current of said transformer, converts the same to the electrical signal corresponding to the currents and derive outputs are installed at optional intervals to distribution lines 12-1-12-n. When a slight ground-fault arises at the point F of the line 12-1, the zero phase current at the point C on the electric power source side of the fault-point F attains IN+ICN+IC2+IC1 and the zero phase current at the point D nearer the load side than the fault point F attains IC1'. A master station 40 receives the signals which the electrical signals proportional to the zero phase currents at the respective points are transmitted from the sub-stations 36-1-36-n, then the master station discriminates that the electrical signals of the substations 36-3 and 36-4 are discontinuous and displays that the slight ground-fault arises in this section.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a method for detecting a ground fault point on an ungrounded power distribution line, and in particular a method for measuring the amount of electricity at any point on a power distribution line in a radial distribution system. This article relates to a method for detecting minute ground faults on railroad tracks.

[Prior art]

Conventionally, the ground fault detection method for radial distribution lines is generally installed in an electrical station 10 as shown in FIG.
(12-1...l2-n) to detect a ground fault and issue an opening command to the breaker 14 (14-1...l4-n) in the fault direction K(k' A re-closing relay i [U device i', 'S 18 and a circuit breaker which starts at the same time as the opening command issued by the ground fault direction relay 16 and outputs a closing command to the vaginal breaker 14 after a predetermined period of time has elapsed. 12 is activated when the circuit is opened and then closed again, and steps in a predetermined period of time until the circuit is opened again.Also installed at arbitrary intervals on the power distribution line 12, there are display devices that activate 1 depending on the presence or absence of line voltage. -1+Y'i! Sectional switch 22 (22-
1...22-n) etc. all installed! The method is such that after detecting a fault, the system operates from 1 m to a ground fault.

117.Y point F
When a ground fault occurs, the current IN flowing toward the fault point F between the ground charging current of the healthy circuits 12-2...12-n and the neutral point of the grounding circuit 11 and the neutral point of the transformer 24. From the failure point F of the circuit to the bus 2]1:, a composite current such as an IL current flows.
The current is converted to the given value by the current engineer. is applied to the ground fault direction relay 16. On the other hand, a zero-sequence voltage vo derived from the tertiary of the grounded instrument transformer 24 is also applied to the ground fault directional relay 16 . The ground fault direction relay 16 is vo, I. Determine whether the phase relationship and its magnitude are greater than a predetermined value,
Breaker 14-1'i is opened and reclosed at the same time relay 1
8.

The section switches 22-1...22-n are the circuit breakers 14-
1 becomes open, the fault point F is isolated from the system, and the ground fault direction relay 16 also returns to its restored state. Next, at a predetermined time after activation, the recloser relay 18 closes the circuit breaker 14-
1, derive the closing command. When the circuit breaker 14-1 is closed, the sectional switches 22-1 and 22-2 are closed in sequence for a predetermined period of time, and if the failure point F is a permanent failure, the sectional switches 22-
At the same time as the circuit 2 is closed, the ground fault direction relay 16 operates to open the circuit breaker 14-1e again. On the other hand, the section indicator 20 is
It is activated at the same time as the breaker is closed for the first time, steps sequentially at a time limit related to the closing time of the section switches 22-1...22-n, and starts stepping at the same time as the breaker 14-1 is opened again. Stop. In other words, the step stop position indicates the failure section.

As described above, in the conventional method Q1, a ground fault in the distribution line is detected using a ground fault directional relay, and the distribution line is made voltage-free.
The method is to operate the ground fault point by applying voltage to the line (4 J' degree) using a fully open and re-closing relay installed in the section switch installed on the line, and measuring the duration of this application.

In other words, in this way, if you investigate the carrier line with no voltage, there will always be a power outage, and in general, in the case of a minor ground fault such as a slight ground fault, if one line is set to no voltage, the fault point will disappear. There are drawbacks such as the fact that it is not possible to detect the point of a fault until it becomes a permanent ground fault, and it is not possible to prevent it before it becomes a full-scale fault.

[Purpose of the invention]

An object of the present invention is to provide a micro-ground fault detection method for detecting a 1111-micro-Gorin ground fault in the distribution line -+lf and the line without making the distribution line voltageless.

[Summary of the invention]

Generally, when a single-wire ground fault occurs in an ungrounded heavy-duty system, the ground-to-ground charging current due to ground-to-ground capacitance has a large effect. The current distribution at this time is shown in FIG.

When a one-line ground fault occurs at point F of distribution line 12-1 in the distribution system in Figure 2, the ground fault current of healthy lines 12-2...12-n is Ic2 and Icn, respectively. enters the busbar 26 and flows toward the accident point F. Accident line 1
2-1, the power supply side current Icl and the load side current Ice' flow toward the fault point F. Since the phases of these 1"ei currents are in phase, their combined value is obtained at the fault point F. In addition, the current IN flowing through the neutral point of the grounding transformer is further combined, that is, the present invention Focusing on the fact that when a one-wire ground fault occurs in a distribution line of a power system, the composite zero-sequence current on the power supply side from the fault point and the zero-sequence current on the load side of the fault line become discontinuous, The present invention is provided with a means for measuring the above-mentioned current at a location, a means for receiving the measured result, and a means for discriminating the ground fault fault section from this value.

[Embodiments of the invention]

The present invention will now be described in detail using the 'core' example shown in FIG.

Is Diagram 3 the Weiike connection point 4 of the radial distribution flL system? N I'j
：Method setting ('i'r: example / example 1, each arrangement /
The supply of magnetic force to the gonads 12-1...12-n is as follows: 1. j
:The newlyweds 14-1.14-2 are supplied from the r source to the bus 26 via the power transformer 30 and further connected to the bus 26.
...l4-nf through each distribution line 12 1 ,
12 2... Supply to 12-n.

The distribution lines 12-1, 12-2...12-n have zero-sequence current transformers j? that derive zero-sequence currents. #32 and the secondary current of the zero-phase current transformer 32 are measured and the current is proportional to this current.7. A slave station 3 comprising a measurement circuit 34 that converts the signal into an electric signal and derives an output.
6 (361, 36'-2...:36-n) are installed 11 at arbitrary intervals. The output from the slave station 36 is transmitted to the 11 station 40 via the communication circuit 38, and the output from the master station is 1,'□! >+ sequentially]IS is compared to determine whether or not there is discontinuity.

In this configuration, if a slight ground fault occurs at point F of distribution αMl 12-1, the zero-sequence current at point C on the power supply side of failure point II' is shown in Figure 4: i) J + Ics + IC2
+Icl, and the zero-sequence current at the point on the load side from the fault point F is I
ce'.

The master station 40 receives signals from the slave stations 36-1, 36-2, . It detects all discontinuities in the electrical signal and indicates that a slight ground fault has occurred in this section.

As described above, according to one embodiment, the zero-sequence current at any point on an ungrounded power distribution line is measured, and the transmitted electrical signal (absolute value of the zero-sequence current, instantaneous or short-term average of the zero-sequence current) is measured. Since the line is compared with the ground fault point (proportional to the value) and is distinguished from the ground fault point in a discontinuous section, it is effective to easily detect the point of a minor ground fault without making the line voltageless. be.

In addition, on ungrounded power distribution lines, ground faults such as deterioration of the insulation of line equipment due to salt damage, defective insulators, and pinhole breakage in insulated cables are initially caused by intermittent ground faults at long intervals.
It is known that the zero-phase-one overflow generally becomes a cylindrical wave, which often progresses and develops into a permanent ground fault. For this reason, No. 1 in Figure 3;
The measurement circuit 34 is provided with means for introducing a zero-sequence current through a filter circuit that passes the five-needle wave flow through the bus, and the four measurement circuits 34iIi and 4iIi absorb the total 111 side of the change in the zero-sequence current. Maximum value of current? Alternatively, the maximum absolute value is memorized and an electrical signal proportional to this is derived. By setting +i'j J, the ground fault is detected and the ground fault point is searched for.
i': This has the effect of preventing permanent ground faults.

〔Effect of the invention〕

As explained above, according to the present invention, &, l: , arrangement′[
0. When insulation deteriorates in a part of the line and a ground fault occurs, instead of leaving the line without voltage, measure the zero-sequence current at point 1 at t and find that this value is discontinuous. Since the area between 14 and 14 is determined to be the ground fault point, even if there is a slight ground fault, the fault area can be reliably searched. It has the effect of making you feel better.

It goes without saying that in this method, even if the residual zero-phase 1d flow that occurs due to system load imbalance is constantly measured, it will not be misjudged based on the above-mentioned principle, and it can be detected with high sensitivity.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing a conventional ground fault protection method for distribution lines, Fig. 2 is a zero-sequence current distribution diagram in the event of a one-wire ground fault on an ungrounded distribution line, and Fig. 3 is an embodiment of the present invention. Figure 4 is a diagram showing the ground fault protection method for distribution lines, and is a zero-sequence current distribution diagram in the event of a one-line ground fault.

Claims (1)

[Claims] 1. A plurality of slave stations installed on the distribution line, which measure the quantity of electricity related to a ground fault in the distribution line, and transmit an electric signal proportional to this quantity of electricity, and receive the transmitted electric signal from the slave station, This micro-ground fault detection method is characterized by being fully equipped with a master station that sequentially compares electrical signals, and by determining discontinuous points in electrical signals as micro-ground fault points.